Aminoglycoside antibiotics, for example, gentamicin, are bound to and transported into the proximal tubule cells in the kidneys [Humes et al., Am. J. Kidney Diseases 11: 5-29 (1982)]. Proximal tubule cell necrosis and subsequent compromise of renal function results [Cronin, Clinical Nephrology 11: 251-256 (1979)]. This nephrotoxicity limits the clinical use of these lifesaving antibiotics [Cronin, Clinical Nephrology 11: 251-256 (1979); Bennett, Mineral Electrolyte Metab. 6: 277-86 (1981); Schor et al., Kidney International 19: 288-296 (1981)]. At present there is no safe means to limit or prevent aminoglycoside nephrotoxicity [Francke et al., Infections in Surgery March:205-214 (1983)].
A number of polyamines, some themselves potentially nephrotoxic, have been shown to inhibit binding and transport of aminoglycoside antibiotics in kidney tissue [Josephovitz et al., J. Pharmacol. Exp. Ther., 223: 314-321 (1982)] or kidney subcellular fractions [spermine--Lipsky et al., J. Pharmacol. Exp. Ther., 215: 390-393 (1980); and polyamines such as spermine, spermidine, polymyxin B and polylysine--Kornguth et al., J. Antimicrob. Chemother., 6: 121-131 (1980)]. However, Josephovitz et al., supra, have questioned the use of organopolycations to reduce the nephrotoxic potential of aminoglycosides because of the possible nephrotoxicity associated with polycations as a class.
Methods for studying the transport of drugs and endogenous substances across epithelial cells such as those in the kidney include the use of isolated membrane vesicles; Murer et al., J. Membrane Biol., 55: 81-95 (1980). Procedures for isolating and purifying brush border membranes from kidney tissue for the use described herein (in vitro membrane transport inhibition screening) have been reported; Williams et al., Toxicology and Applied Pharmacology, 61: 243-251 (1981) and Kinsella et al., Biochimica et Biophysica Acta., 552: 468-477 (1979). Gentamicin transport/binding studies using isolated renal membrane vesicles have been reported; Lipsky et al., supra, Sastraskih et al., J. Pharmacol. Exp. Ther., 222: 350-358 (1982); kidney mitochondrial and microsomal binding inhibition have also been employed; Kornguth et al., supra. Josephovitz et al., supra, have conducted in vivo studies of inhibition of gentamicin uptake in rat renal cortex by organic polycations.
Applicants have found that certain neutral and anionic polyamino acids prevent or retard the membrane transport (in vitro) and nephrotoxicity (in vivo) of aminoglycoside antibiotics. Previously, only polycations have been reported to inhibit renal membrane binding or tissue accumulation of aminoglycosides. Reports of aminoglycoside nephrotoxicity inhibitors have been confined to unrelated substances such as fosfomycin [Inouye et al., J. Pharm. Dyn., 5: 659-669 (1982)], glucarolactones/glycarolactams [Furunto et al., Japan J. Pharmacol., 27: 371-378 (1977); J. Antibiotics, 29: 950-953 (1976); Furunto et al., J. Antibiotics, 29: 187-194 (1976); U.S. Pat. No. 4,122,171; U.S. Pat. No. 3,929,583, U.S. Pat. No. 3,962,429] and sodium formaldehyde bisulfite [Pindell et al., Chemotherapia., 8: 163-174 (1964); British Pat. No. 957,433; German OS Nos. 2,641,388].